Many golf balls are commercially selling, but they are typically classified into solid golf balls (such as, two-piece solid golf balls) and thread wound golf balls. The solid golf ball consists of a solid core of molded rubber material and a cover of thermoplastic resin (e.g. ionomer resin) covering the solid core. The thread wound golf ball consists of a solid or liquid center, a thread wound layer formed the center and a cover of ionomer resin or balata etc. having a thickness of 1 to 2 mm covering on the thread wound layer. The solid golf ball, when compared with the thread wound golf ball, has better durability and better flight performance because of a larger initial velocity when struck, and a longer flight distance. The solid golf ball is generally approved or employed by many golfers, especially amateur golfers. On the other hand, the solid golf ball exhibits a hard shot feel when hit, and shows difficulty when trying to spin the ball, thus exhibiting poor controllability at approach shot. The difficulty of putting spin on the ball comes from the structural features of the solid golf ball whereas the ball velocity is very high, when hitting, and a contact area of the ball with a hitting face of a golf club is very small. Thus, the solid golf ball is not approved of or employed by professional golfers or high level amateur golfers who attach importance to shot feel and controllability of the approach shot.
In order to improve controllability and shot feel of the solid golf ball, it has been attempted to soften the cover of the solid golf ball by various means. However, softening of the cover adversely degrades the rebound characteristics of the ball, and reduces flight distance, because the launch angle is low and the spin amount is high causing a high trajectory when hit by a driver or a long iron club.